Rapid prototyping systems are now under development in an attempt to provide single automated systems which can produce prototypes and small production runs directly from engineering drawings. There are currently several types of such systems, some of which types are described in the background section of U.S. Pat. No. 5,398,193 of deAngelis, which section is incorporated herein by reference thereto.
As discussed in the referenced patent, the typical system includes a source of material, a material deposition system such as a nozzle, a material receiving platform, and means for moving the platform in at least three directions with respect to the deposition system under the control of a computer. The material typically flows through the nozzle as either a powder or a liquid and is hardened by some process when it hits the platform or a previous hardened layer of material. Objects are formed by spraying and hardening successive slices of the final object.
For systems based on depositing a colloidal slurry, the ideal system would permit a rapid flow of material from the nozzle and even distribution of material, with rapid solidification, when the material strikes a surface. Furthermore, as multiple layers are applied, they must flow together sufficiently to form a unitary structure, but not flow so much as to distort the shape of the structure. Lastly, the deposited structure should be relatively quickly hardened to a final form that is free of voids.
Typical slurry systems known in the art rely on photopolymerizable, thermoplastic, acrylate, or epoxy additives that cause the slurry to transform into a rigid mass after the slurry has been dispensed from an orifice. These additives comprise from 40 to 70% of the volume of the deposited slurry, resulting in either a significant change in volume or significant voids in the structure after the additives-are removed prior to sintering. Furthermore, to prevent cracking, these non-volatile organic additives must be removed very slowly. This process typically involves heating the samples carefully for several days to burn off the additives.
It is an object of this invention to provide a method for rapid prototyping with less than 10% volume, and preferably less than 0.5% volume, of organic binders.
It is a further object of this invention to provide a slurry-for rapid prototyping which has a sufficient volume of solids to be pseudoplastic, and less than 10% volume organic binders.
Additional objects, advantages, and novel features of the invention will become apparent to those skilled in the art upon examination of the following description or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purpose of the present invention, as embodied and broadly described herein, the present invention may comprise a method for rapidly prototyping a part from a material, the method comprising forming a pseudoplastic slurry, depositing a bead of the pseudoplastic slurry through a nozzle onto a surface that moves with respect to the nozzle, and removing liquid from the bead as it is deposited to cause the bead to become dilatant. The slurry consists of a volatile liquid, no more than 10 volume percent nonvolatile binders and dispersants, and insoluble particles of the predetermined material. The slurry becomes dilatant upon deposition by the system in a drying environment.